Introducer sheaths are well-known devices which can be used to introduce catheters through body conduits into the human body. Introducer sheaths are often used to facilitate the insertion of catheters into body vessels where placement of the catheter without an introducer sheath may present difficulty. Sheaths are useful where the tract to be traversed is tortuous or obstructed. Introducer sheaths are commonly used in applications where backflow of bodily fluids through the introducer sheath does not present a problem. Typical applications do not include insertion of the sheath into blood vessels, where backflow of blood through the sheath can present a problem. For this reason, introducer sheaths have seen limited use in vascular applications.
When catheters are inserted into the vasculature, such as into an artery near the groin as in Percutaneous Transluminal Angioplasty (PTCA) procedures, there is substantial blood pressure within the artery. The catheter is typically sealed at the point of insertion to prevent outflow around the inserted catheter. Any internal catheter back-flow is typically prevented using proximal end manifolds having attached Luer fittings, Tuohy-Borst closures, stop cocks, and other reversibly closeable devices.
Introducer sheaths are often introduced over a previously inserted guide wire. As sheaths are sometimes very flexible and the target pathway very tortuous, a coaxially tapered dilator is often used in conjunction with the introducer sheath for the purpose of advancing the sheath to the target site. The dilator can be withdrawn after the introducer sheath is in position. After a catheter has been advanced through the introducer sheath, the sheath has usually served its purpose and can be removed. If the sheath were not a peel-away sheath, removal over the inserted catheter and proximal catheter manifold could prove difficult. A peel-away sheath provides a means for removing the sheath by peeling it away from the catheter it surrounds, typically by tearing the sheath apart in halves, in opposite directions transversely away from the catheter.
In order to peel away the sheath, any sheath proximal end fixture must typically be peeled away or broken away as well. In applications where backflow is not a major problem, this is not a major issue as the sheath proximal end can be open and the proximal fixture, if any, is minimal. In vascular applications, where blood pressure makes backflow through the sheath a problem, the proximal fixture should include a valve that is able both to substantially restrict blood backflow and to admit an inserted catheter.
What would be desirable is a valve for use with peel-away introducer sheaths where the valve can be open, shut, and broken apart for removal from the inserted catheter. What would be advantageous is a breakaway valve for an introducer sheath which also minimizes backflow during introduction of a catheter through the valve.